Jeong Sanghyup, Marks Bradley P, James Michael K
Biosystems and Agricultural Engineering Department, Michigan State University, East Lansing, Michigan 48824, USA.
J Food Prot. 2017 Jan;80(1):169-176. doi: 10.4315/0362-028X.JFP-16-224.
Ongoing regulatory changes are increasing the need for reliable process validation methods for pathogen reduction processes involving low-moisture products; however, the reliability of various validation methods has not been evaluated. Therefore, the objective was to quantify accuracy and repeatability of four validation methods (two biologically based and two based on time-temperature models) for thermal pasteurization of almonds. Almond kernels were inoculated with Salmonella Enteritidis phage type 30 or Enterococcus faecium (NRRL B-2354) at ~10 CFU/g, equilibrated to 0.24, 0.45, 0.58, or 0.78 water activity (a), and then heated in a pilot-scale, moist-air impingement oven (dry bulb 121, 149, or 177°C; dew point <33.0, 69.4, 81.6, or 90.6°C; v = 2.7 m/s) to a target lethality of ~4 log. Almond surface temperatures were measured in two ways, and those temperatures were used to calculate Salmonella inactivation using a traditional (D, z) model and a modified model accounting for process humidity. Among the process validation methods, both methods based on time-temperature models had better repeatability, with replication errors approximately half those of the surrogate ( E. faecium ). Additionally, the modified model yielded the lowest root mean squared error in predicting Salmonella inactivation (1.1 to 1.5 log CFU/g); in contrast, E. faecium yielded a root mean squared error of 1.2 to 1.6 log CFU/g, and the traditional model yielded an unacceptably high error (3.4 to 4.4 log CFU/g). Importantly, the surrogate and modified model both yielded lethality predictions that were statistically equivalent (α = 0.05) to actual Salmonella lethality. The results demonstrate the importance of methodology, a, and process humidity when validating thermal pasteurization processes for low-moisture foods, which should help processors select and interpret validation methods to ensure product safety.
持续的法规变化使得对涉及低水分产品的病原体减少过程的可靠工艺验证方法的需求日益增加；然而，各种验证方法的可靠性尚未得到评估。因此，目标是量化杏仁热巴氏杀菌的四种验证方法（两种基于生物学方法和两种基于时间 - 温度模型）的准确性和可重复性。将杏仁仁接种肠炎沙门氏菌30型噬菌体或粪肠球菌（NRRL B - 2354），接种量约为10 CFU/g，平衡至水分活度（a）为0.24、0.45、0.58或0.78，然后在中试规模的湿空气冲击烤箱中加热（干球温度121、149或177°C；露点<33.0、69.4、81.6或90.6°C；风速v = 2.7 m/s）至目标致死率约4个对数。通过两种方式测量杏仁表面温度，并使用传统的（D，z）模型和考虑工艺湿度的修正模型，根据这些温度计算沙门氏菌的灭活情况。在工艺验证方法中，两种基于时间 - 温度模型的方法具有更好的可重复性，其重复误差约为替代菌（粪肠球菌）的一半。此外，修正模型在预测沙门氏菌灭活方面产生的均方根误差最低（1.1至1.5 log CFU/g）；相比之下，粪肠球菌产生的均方根误差为1.2至1.6 log CFU/g，而传统模型产生的误差高得不可接受（3.4至4.4 log CFU/g）。重要的是，替代菌和修正模型得出的致死率预测与实际沙门氏菌致死率在统计学上等效（α = 0.05）。结果表明，在验证低水分食品的热巴氏杀菌过程时，方法、水分活度和工艺湿度的重要性，这将有助于加工商选择和解释验证方法以确保产品安全。
